Field of the Invention
The present invention relates generally to sweetener compositions comprising mainly highly purified steviol glycosides and methods for making and using them as a sweetener and flavor modifier in various food and beverage products. The invention also relates to a combination of selective Steviol Glycosides from Stevia rebaudiana Bertoni plant extract to make the sweetness profile more rounded and sugar-like, and more particularly, this invention describes the mixture of three major steviol glycosides, namely Rebaudioside D, Rebaudioside B and Rebaudioside A of different ratio to provide rounded sweetness profile in reduced or no sugar added food and beverage products.
Description of the Related Art
Nowadays sugar alternatives are receiving increasing attention due to awareness of many diseases in conjunction with consumption of high-calorie foods and beverages. Food and beverage industry is being challenged to produce healthier, reduced calorie foods to meet the demands of consumers and public policy officials. The food industry is faced with the challenge of making more natural, ‘better for you’ foods and beverages that fit consumer trends, while achieving great taste necessary for successful products. Low-calorie sweetening ingredients have expanded options for consumers looking to reduce calories and sugar levels in their diets, but these ingredients can be limited by taste, stability and versatility. The consumer perception of artificial nature and safety concerns of such sweeteners is not helping the cause either.
Therefore non-caloric sweeteners of natural origin are becoming increasingly popular. The stevia leaf extract from Stevia rebaudiana Bertoni, a centuries-old sweet herb, provides a unique zero calorie option that overcomes some of the barriers seen with other low-calorie sweeteners. Stevia plant produces a number of diterpene glycosides, commonly known steviol glycosides, which feature high intensity sweetness and sensory properties superior to those of many other high potency sweeteners.
The above-mentioned sweet glycosides, have a common aglycon, steviol, and differ by the number and type of carbohydrate residues at the C13 and C19 positions. The leaves of Stevia are able to accumulate up to 10-20% (on dry weight basis) steviol glycosides. The major glycosides found in Stevia leaves are Rebaudioside A (2-10%), stevioside (2-10%), and Rebaudioside C (1-2%). Other glycosides such as Rebaudioside B, D, E, and F, steviolbioside and rubusoside are found at much lower levels (approx. 0-0.2%).
Steviol glycosides differ from each other not only by molecular structure, but also by their taste properties. Usually stevioside is found to be 110-270 times sweeter than sucrose, Rebaudioside A between 150 and 320 times, and Rebaudioside C between 40-60 times sweeter than sucrose. Dulcoside A is 30 times sweeter than sucrose. Rebaudioside A has the least astringent, the least bitter, and the least persistent aftertaste thus possessing the most favorable sensory attributes in major steviol glycosides (Tanaka O. (1987) Improvement of taste of natural sweeteners. Pure Appl. Chem. 69:675-683; Phillips K. C. (1989) Stevia: steps in developing a new sweetener. In: Grenby T. H. ed. Developments in sweeteners, vol. 3. Elsevier Applied Science, London. 1-43). The chemical structure of Rebaudioside A is shown in FIG. 1.
Methods for the extraction and purification of sweet glycosides from the Stevia rebaudiana plant using water or organic solvents are described in, for example, U.S. Pat. Nos. 4,361,697; 4,082,858; 4,892,938; 5,972,120; 5,962,678; 7,838,044 and 7,862,845.
However, even in a highly purified state, steviol glycosides still possess undesirable taste attributes such as bitterness, sweet aftertaste, licorice flavor, etc. It was shown that these flavor notes become more prominent as the concentration of steviol glycosides increases (Prakash I., DuBois G. E., Clos J. F., Wilkens K. L., Fosdick L. E. (2008) Development of Rebiana, a natural, non-caloric sweetener. Food Chem. Toxicol., 46, S75-S82).
Rebaudioside B (CAS No: 58543-17-2), or Reb B, also known as stevioside A4 (Kennelly E. J. (2002) Constituents of Stevia rebaudiana In Stevia: The genus Stevia, Kinghorn A. D. (Ed), Taylor & Francis, London, p. 71), is one of the sweet glycosides found in Stevia rebaudiana. Sensory evaluations show that Reb B was approximately 300-350 times sweeter than sucrose, while for Reb A this value was approximately 350-450 (Crammer, B. and Ikan, R. (1986) Sweet glycosides from the Stevia plant. Chemistry in Britain 22, 915-916, and 918). The chemical structures of Rebaudioside A and Rebaudioside B are shown in FIG. 1.
It was believed that Reb B forms from partial hydrolysis of Rebaudioside A during the extraction process (Kobayashi, M., Horikawa, S., Degrandi, I. H., Ueno, J. and Mitsuhashi, H. (1977) Dulcosides A and B, new diterpene glycosides from Stevia rebaudiana. Phytochemistry 16, 1405-1408). However further research shows that Reb B occurs naturally in the leaves of Stevia rebaudiana and currently it is one of nine steviol glycosides recognized by FAO/JECFA (United Nations' Food and Agriculture Organization/Joint Expert Committee on Food Additives) in calculating total steviol glycosides' content in commercial steviol glycosides preparations (FAO JECFA (2010) Steviol Glycosides, Compendium of Food Additive Specifications, FAO JECFA Monographs 10, 17-21). On the other hand, the water solubility of Reb B is reported to be about 0.1% (Kinghorn A. D. (2002) Constituents of Stevia rebaudiana In Stevia: The genus Stevia, Kinghorn A. D. (Ed), Taylor & Francis, London, p. 8). In many food processes where highly concentrated ingredients are used, a highly soluble form of Reb B will be necessary.
Rebaudioside D (CAS No: 63279-13-0), as shown in FIG. 2, is one of the sweet glycosides found in Stevia rebaudiana. Studies show that highly purified forms of Rebaudioside D (Reb D) possess a very desirable taste profile, almost lacking the bitterness and lingering licorice aftertaste typical for other Steviol glycosides.
These desired sensory properties of Reb D attract great interest for methods of preparation of highly purified forms of Rebaudioside D. However, highly purified steviol glycosides possess relatively low water solubility. For example Rebaudioside A (Reb A) thermodynamic equilibrium solubility at room temperature is only 0.8%. On the other hand, the water solubility of Reb B is reported to be about 0.1% and that of Reb D is even lower, only at 0.01-0.05% at room temperature (Kinghorn A. D. (2002) Constituents of Stevia rebaudiana In Stevia: The genus Stevia, Kinghorn A. D. (Ed), Taylor & Francis, London, p. 8). Reb B or Reb D can be solubilized at higher concentrations at a higher temperature, but they will quickly crystallize back from solution upon cooling to room temperature. Considering high sweetness intensity of steviol glycosides (100-300 times of sugar sweetness)—even 0.05% solubility may seem sufficient for many applications.
Many food production processes use highly concentrated ingredient mixes prior to producing final forms of food products. In that case, higher concentrations of dissolved Reb A, Reb D and Reb B will be required. It has to be noted that using the heat for dissolution of such sweeteners may not be possible in many compositions which contain heat sensitive components. Also maintaining high temperature of mixture for prolonged time to prevent premature crystallization of Rebaudioside A, B, D can cause thermal degradation of mixture components or undesirable changes of organoleptic properties.
Therefore there is a need for developing highly soluble forms or compositions of sweetener molecules which can provide stable solutions with minimal or no heat treatment. The patent applications WO/2012/109506 and WO/2013/036366 outline the methodology for making highly soluble Reb A and Reb D compositions, respectively. The invention relates to a process for producing highly soluble compositions containing purified steviol glycosides from Stevia rebaudiana Bertoni plant extract, more particularly the combination of Reb A, Reb D and Reb B.
In this invention, a process is developed to make a mixture of or Reb D, Reb A and Reb B with or without small amount of other steviol glycosides. The process involved precise control of pH, temperature and time to achieve blends of different ratios of Reb D, Reb A and Reb B and to make the mixer more soluble than a mechanical blend of Reb D, Reb A and Reb B.
Within the description of this invention we will show that, when applied in specific manner, certain blend of Reb D with other steviol glycosides, especially Reb A and Reb B, may impact the taste profile and offer significant advantages for stevia sweeteners' use in various food and beverage applications.